There are a lot of insect pests that don’t thrive in New Hampshire because of our cold winters. Our winters are getting less cold, or at least less long, and some of them are sneaking north with dire consequences.

One of those is the hemlock wooly adelgid, which has devastated hemlock forests down south and is showing up in increasing numbers here.

Every time there’s a real cold snap, I hope that invasive bugs like the adelgid will be knocked back. So I was interested when I saw a USDA research paper on the effects of the “polar vortex,” a cold snap in 2014 so brutal that it almost brought our electric grid to its knees, on the adelgid.

Alas, the conclusion is: “estimated that the 2014 cold wave resulted in at least a 238% decrease in its population growth rate. However, we also observed that the detrimental effect of the 2014 cold wave to A. tsugae was short-lived, as populations measured in the late summer of 2014 rebounded to pre-2014 cold wave densities.”

Darn you, insect world!

Here’s the paper.

(A mathematical note: A “238 percent decrease” is a really weird way – I’d say an incorrect way – to put it. I assume they mean that the 2013 growth rate was 2.38 time the 2014 growth rate.)


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